Rosen type piezoelectric transformer with multiple output electrodes, and stabilizer for multiple light source using that

ABSTRACT

The present invention is disclosed a piezoelectric transformer with multiple outputs for lighting a plurality of cold cathode fluorescent lamps at the same time by forming a plurality of output electrodes as one body and a stabilizer having the piezoelectric transformer with multiple output electrodes. The piezoelectric transformer includes a piezoelectric plate; an input electrode formed on an upper surface of the plate; a plurality of output electrodes having an identical band shape, arranged in equal distance in the longitudinal direction of the plate at an outer side of the input electrode, and connected electrically to one ends of the plurality of the cold cathode fluorescent lamps respectively; and a common electrode formed on a bottom surface of the plate, confronting to the input electrode, commonly connected to ground of the stabilizer and other ends of the plurality of the cold cathode fluorescent lamps.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to Rosen type PiezoelectricTransformer constituting a stabilizer for cold cathode fluorescent lampbeing used for back light of liquid crystal display (LCD) device, moreparticularly, to a Rosen type Piezoelectric Transformer with multipleoutput electrodes for lighting a plurality of cold cathode fluorescentlamp at the same time by forming multiple output electrodes as one bodyand a stabilizer for multiple light source using that.

[0003] 2. DESCRIPTION OF THE PRIOR ART

[0004] As well known to those skilled in the art, a fluorescent lampneeds high voltage at initial lighting in order to emit required thermalelectrons for an electric discharge. And, after electric discharge, thevoltage impressed on the fluorescent lamp has negative resistancecharacteristics reduced when lamp current increases.

[0005] Especially, a cold cathode fluorescent lamp being used forbacklight of liquid crystal display (LCD) device is fight source usingcold emission (electron emission caused by forcing strong electric fieldto cathode surface). In order to light the Backlight comprised of thecold cathode fluorescent lamp, it needs about 500 V need. And,generally, a step-up transformer is used for convert the commercial ACpower source to the driving voltage.

[0006] The stabilizer is a lamp lighting device applying the drivingvoltage for lighting on the fluorescent lamp with properties mentionedabove, and comprises, as shown in FIG. 6, rectifying section 621 whichrectifies AC commercial source 61 to DC voltage in some level, powerfactor compensation section 622 compensating for the power factor causedby the fluctuation of AC commercial voltage source in respect of theoutput voltage of the rectifying section 621, AC voltage generatingsection 623 converting the DC voltage inputted through the power factorcompensation section 622 to proposed AC voltage of high frequency, and aresonating section 624 for resonating with the output voltage of a ACvoltage generating section 623 and supplying the AC voltage on thefluorescent lamp 63.

[0007] As above-mentioned, AC voltage generating section 623 is calledan inverter.

[0008] And, said resonating section 624 is conventionally constructed togenerate the resonance by the inductance of the winding type transformerand the capacitance of a resonance capacitor with connection of thewinding type transformer. But the winding type transformer has someproblems that the rate of producing poor quality is high and thecredibility of the stabilizer is reduced because the deviation of thequality of core is excessive, so said winding type transformer isrecently replaced with a piezoelectric transformer such that theresonance is generated by the inductance of the inductor with thecapacitance of the piezoelectric transformer.

[0009] But the above statement is the case of connecting one fluorescentlamp to one stabilizer. On the other hand, in case of lighting more thantwo fluorescent lamps by connecting the fluorescent lamps into onestabilizer, if one of numerous fluorescent lamps is lighted, otherfluorescent lamps connected to the wound-type transformer in parallel isnot lighted because a lower voltage is supplied to the other fluorescentlamps by lighting the one fluorescent lamp.

[0010] Accordingly, in the case of connecting two or more fluorescentlamps to the one stabilizer, as shown in FIG. 8 and 9, the ballastcapacitor is directly connected between fluorescent lamps 72, 82 andtransformers 712, 812 such that the voltage required for initiallightening is impressed on the fluorescent lamp even if a certainfluorescent lamp is lighted ahead.

[0011] Hence, the conventional stabilizer used for a plurality of lightsources is constructed as shown in FIG. 8 and 9.

[0012] As shown in FIG. 8, the stabilizer comprises a circuit section711, which includes the rectifying section 621, the power compensatingsection 622, the AC voltage generating section 623, and the resonancecapacitor of the resonating section 624, the piezoelectric transformer712 of which input electrode is connected to the resonance capacitor ofthe circuit section 711, and a plurality of ballast capacitors 713 beingconnected to output electrode of the piezoelectric transformer 712 inparallel. Wherein the number of ballast capacitors is same that oflamps. Furthermore, a plurality of fluorescent lamps 72 is connected toother terminal of the plurality of ballast capacitors 713 of thestabilizer 71 respectively.

[0013] As shown in FIG. 9, the stabilizer for a plurality of fluorescentlamps having a wound-type transformer comprises a circuit section 811,which includes the rectifying section 621, the power compensatingsection 622, the AC voltage generating section 623, and the resonancecapacitor of the resonating section 624. And the stabilizer comprisesthe wound-type transformer 812 of which input electrode is connected toa resonance capacitor of the circuit section 811, and a plurality ofballast capacitors 813 being connected to output electrode of thewound-type transformer 812 in parallel. Furthermore, the plurality offluorescent lamps 82 is connected to other terminal of the plurality ofballast capacitors 713 of the stabilizer 71 respectively.

[0014] In the stabilizer above, because AC voltage supplied by thewound-type transformer 712 or the piezoelectric transformer 812 isdivided equally among the plurality of fluorescent lamps via the ballastcapacitor 713,813, the plurality of fluorescent lamps can be lighted atthe same time. Wherein the ballast capacitor 713,813 has a highwithstand voltage characteristic, and its size is also big.

[0015] Accordingly, as shown in FIG. 7 or FIG. 8, because the stabilizerneeds the ballast capacitors in proportion to the number of theconnected fluorescent lamp, a volume and the number of componentsincrease, and a cost increases also.

[0016] Thus, in the case of constituting a stabilizer as mentionedabove, there have been some problems that numbers of components and thevolume increase and the production cost rise because a ballast capacitoris required proportion to numbers of connected fluorescent lamp.

SUMMARY OF THE INVENTION

[0017] Accordingly, an object of the present invention is to provide aRosen type piezoelectric transformer having a plurality of outputelectrodes with uniform output property which makes the fluorescent lamplight stably, the operation be simple, and the cost be reduced. thepresent invention provides a Rosen type Piezoelectric Transformer withmultiple output electrodes, being used for a stabilizer to light aplurality of cold cathode fluorescent lamps, comprising: a piezoelectricplate; an input electrode formed at an upper surface of the plate; aplurality of output electrodes having an identical band shape, arrangedin equal distance in the longitudinal direction of the plate at an outerside of the input electrode, and connected electrically to one ends ofthe plurality of the cold cathode fluorescent lamps respectively; and acommon electrode formed at a bottom surface of the plate, confronting tothe input electrode, commonly connected to ground of the stabilizer andother ends of the plurality of the cold cathode fluorescent lamps.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

[0019]FIG. 1 shows a perspective view of a stabilizer for a plurality oflamps having a Rosen type Piezoelectric Transformer in accordance withthe primary embodiment of the present invention;

[0020]FIG. 2 shows a perspective view of the Piezoelectric Transformerin accordance with the present invention in FIG. 1;

[0021]FIG. 3 shows a perspective view of a Rosen type PiezoelectricTransformer in accordance with another embodiment of the presentinvention and a stabilizer for lighting four lamps;

[0022]FIG. 4 shows a perspective view of the modified PiezoelectricTransformer as shown in FIG. 3;

[0023]FIG. 5 shows a perspective view of a Rosen type PiezoelectricTransformer in accordance with another embodiment of the presentinvention and a stabilizer for a plurality of lamps applying that;

[0024]FIG. 6 shows a perspective view of the modified PiezoelectricTransformer as shown in FIG. 5;

[0025]FIG. 7 shows a block diagram of a conventional fluorescent lampstabilizer;

[0026]FIG. 8 shows a perspective view of a stabilizer for a plurality oflamps applying a conventional winding type piezoelectric transformer;and

[0027]FIG. 9 shows a perspective view of a stabilizer for a plurality oflamps applying a conventional piezoelectric transformer.

DETAILED DESCRIPTION OF THE INVENTION

[0028] Reference now should be made to the drawings, in which the samereference numerals are used throughout the different drawings todesignate the same or similar components.

[0029]FIG. 1 shows a view of an embodiment of a piezoelectrictransformer and a stabilizer using the piezoelectric transformer, inthis embodiment the 2 light sources is used.

[0030] As shown in FIG. 1, a Rozen type piezoelectric transformer 10comprises an input electrode 3 formed at the center of the upper surfaceof the piezoelectric plate 1 in the longitudinal direction of the plateand connected to a circuit section 2 of a stabilizer 100, a commonelectrode 7 formed on the bottom surface of the piezoelectric plate 1opposed to the input electrode 3, and two output electrodes 6 formed onthe both confronting side surface in the longitudinal direction of theplate 1.

[0031] And, the input electrode 3 and the common electrode 7 areconnected to an output of the circuit section 2 in the stabilizer 100,the two output electrode 6 is respectively connected to one ends of twocold cathode fluorescent lamps 4 of a lamp section 200, and the otherends of two cold cathode fluorescent lamps 4 is connected to the commonelectrode 7. That is, two cold cathode fluorescent lamps 4 are connectedto the piezoelectric transformer 10 in parallel.

[0032] As described above, the circuit section 2 converts the commercialvoltage source of 220 V or 110 V with AC voltage of a predeterminedvoltage level and frequency. And then The AC voltage is impressed theinput electrode 3 and the common electrode 7. As result, it brings abouta longitudinal vibration. The longitudinal vibration is transmitted theoutput electrodes 6, and then a AC voltage outputs between the outputelectrodes 6 and the common electrode 7. The AC voltage outputted theoutput electrodes 6 is related to the distance to the input electrode 3and the thickness of the piezoelectric plate 1, and the outputelectrodes 6 placed on the confronting side surface has the same outputproperty because each of the output electrodes 6 has the same condition.Thus, the uniform voltage is impressed to two cold cathode fluorescentlamps 4 such that all of the fluorescent lamp 4 can be lighted.

[0033]FIG. 2 shows a perspective view of the modified PiezoelectricTransformer as shown in FIG. 1. The piezoelectric transformer is made bymulti-layering first piezo-sheet 8 printing the input electrode 3 on thesurface and second piezo-sheet 8′ printing the common electrode 7 on thesurface in turns. The input electrodes 3 on first piezo-sheet 8 isconnected each other and the common electrode 7s on second piezo-sheet8′ is connected each other.

[0034]FIG. 3 and 4 show perspective views of a Piezoelectric Transformerin accordance with an embodiment of the present invention and astabilizer for 4 light sources applying that.

[0035] As shown in the drawings, the piezoelectric transformer has aninput electrode 3 formed at the center of the upper surface of thepiezoelectric plate 1 in the direction of its width.

[0036] In multi-layer type, the input electrode 3 and the outputelectrodes 6 is formed on the surface of a piezo-sheet. The inputelectrode 3 is connected to the circuit section 2.

[0037] And, Four output electrodes 6 is formed to the positions dividedinto equal distance on the upper surface and the both confronting sidesurface in longitudinal direction. And the common electrode 7 is formedon a the bottom surface of the piezoelectric plate 1 opposed to theinput electrode 3.

[0038] The input electrode 3 is connected to the output of generating ACvoltage of the circuit section 2. The four output electrodes 6 areconnected to the one ends 5A of the cold cathode fluorescent lamps 4.And the other ends 5B of the cold cathode fluorescent lamps 4 and theground of the circuit section 2 are connected to the common electrode 7.Additionally, FIG. 5 and 6 show perspective views of a piezoelectrictransformer in accordance with another embodiment of the presentinvention. In FIG. 5, an input electrode 3 is formed at one end of theupper surface of the plate 1 in the longitudinal direction of thepiezoelectric plate 1, and connected to the circuit section 2. Theoutput electrodes 6 is formed on a side surface of the piezoelectricplate 1 in a direction of thickness of the plate and is formed on aupper surface in a band shape, being arranged in an equal distance. And,the common electrode 7 is formed on the bottom surface of thepiezoelectric plate 1 opposed to the input electrode 3 and is connectedto the AC voltage generator 2 and the other ends 5B of the plurality ofthe cold cathode fluorescent lamps 4 at the same time.

[0039] In FIG. 6, the input electrode 3 connected to the circuit section2 and the output electrodes 6 is formed on the surface of a piezo-sheet,and the common electrode 7 is formed on the surface of the otherpiezo-sheet. And a piezo-sheet formed the input electrode 3 and outputelectrods 6, and the other piezo-sheet formed the common electrode 7 islayered in turns.

[0040] The operational effect of the present invention will be describedherein below.

[0041] In order to satisfy restricting the noise, lowering the spendingpower, making the device miniaturization, and the like, a piezoelectrictransformer having the piezoelectric effect is used.

[0042] The basic principle of the piezoelectric transformer is thefollowing. A deformation of another section of the piezoelectrictransformer is generated due to a deformation generated by impressing avoltage to one section of the piezoelectric transformer, and a secondvoltage is then generated on another section. The principle above isapplied to the Rosen type, which is the simplest type.

[0043] A piezoelectric plate is formed by stacking a plurality of sheetsto which internal electrodes is printed in some patterns and stacked, anexternal input electrode is formed on one longitudinal side of upper andbottom surface of the piezoelectric plate, and an output electrode isformed at a confronting position of the input section on the side of thepiezoelectric plate.

[0044] If the voltage having resonance frequency is impressed to theexternal output electrode, a longitudinal vibration mode is generated inthe internal electrode, and the longitudinal vibration is generated inthe output electrode formed on the side surface of the piezoelectricplate by the generated longitudinal vibration mode, and the voltage isgenerated in the output electrode as a piezoelectric effect occurred bythe produced stress. And then the voltages of the output terminal rise.

[0045] As shown in the FIG. 1 and 2, the input electrode 3 and thecommon electrode 7 formed on the upper and bottom surface of thepiezoelectric plate 1 are connected to the AC voltage generator 2. If avoltage having a resonance frequency from the AC voltage generator 2 issupplied to the input electrode 3 and the common electrode 7, the outputelectrode 6 formed on both side of the piezoelectric plate 1 vibrates isgenerated in a direction of length by longitudinal vibration mode.

[0046] A voltage is applied to the output electrode 6 by thepiezoelectric effect produced by the stress of the piezoelectric plate1, and a high voltage is impressed on the cold cathode fluorescent lamp4 connected through the terminal 5A.

[0047] And the same voltage is impressed through the common electrode 7placed in the bottom surface of the piezoelectric plate 1, which isformed at confronting position of the input electrode 3, and the commonelectrode 7 is connected to the AC voltage generator 2 and the otherterminals 5B of a plurality of the cold cathode fluorescent lamps 4 suchthat the cold cathode lamp 4 is impressed a high voltage.

[0048] In addition, as shown in the FIG. 3 and 4, the resonancefrequency is impressed by means of inputting the input electrode 3 andthe common electrode 7 placed in the upper and bottom surface of thepiezoelectric plate 1 or made from stacking into the AC voltagegenerator 2. Then the longitudinal vibration mode occurs in the internalsection, and this makes the longitudinal vibration in the direction oflength of the multiple output electrodes 6 placed on the both surface ofthe piezoelectric plate 1 and the surface of the input electrode 3.

[0049] A voltage is applied to the output electrode 6 by thepiezoelectric effect produced by the stress, and boosting is produced toimpress high voltage on the cold cathode fluorescent lamp 4 connectedthrough the terminal 5A.

[0050] And the same voltage is impressed through the common electrode 7placed on the bottom surface of the piezoelectric plate 1, which isformed at confronting position of the input electrode 3, and the commonelectrode 7 is connected to the AC voltage generator 2 and the otherterminals 5B of a plurality of the cold cathode fluorescent lamps 4 suchthat the cold cathode lamp 4 is impressed a high voltage.

[0051] Accordingly, it is possible to reduce the number of thecomponents and minimize the size of the inverter by using thepiezoelectric transformer with multiple outputs of the presentinvention, and this removes the retraction of designing and the needs ofinstallation of high internal voltage condenser, an additional groundingequipment is also unnecessary.

[0052] Accordingly, it is possible to generate a multiple output voltagehaving an uniform output property by using the multiple outputelectrodes. Thus, by providing a cold cathode fluorescent lamp using thepiezoelectric transformer with multiple outputs, a easy working and acost savings may be realized without an additional ballast capacitor.

[0053] Finally, by minimizing a volume of stabilizer, a designrestriction of the stabilizer may be lower, and it is not necessary todesign about the isolation additionally.

[0054] In addition, multiple outputs are easily obtained by applying thepiezoelectric transformer of the present invention and various vibrationmodes (including length type, width type, area type, radial type, ringtype vibration mode, and the like) to a power converting circuit (forexample, DC-DC converter, AC-DC converter, DC-AC converter) transmittinga power.

[0055] Although various embodiments of this invention have been shownand described, it should be understood that variations, modificationsand substitutions, as well as rearrangements and combinations of thepreceding embodiments can be made by those skilled in the art withoutdeparting from the novel spirit and scope of this invention.

What is claimed is:
 1. A Rosen type Piezoelectric Transformer withmultiple output electrodes, being used for a stabilizer to light aplurality of cold cathode fluorescent lamps, comprising: a piezoelectricplate; an input electrode formed on an upper surface of the plate; aplurality of output electrodes having an identical band shape, arrangedin equal distance in the longitudinal direction of the plate at an outerside of the input electrode, and connected electrically to one ends ofthe plurality of the cold cathode fluorescent lamps respectively; and acommon electrode formed on a bottom surface of the plate, confronting tothe input electrode, commonly connected to ground of the stabilizer andother ends of the plurality of the cold cathode fluorescent lamps.
 2. ARosen type Piezoelectric Transformer with multiple output electrodesaccording to claim 1, wherein said input electrode is formed at centerof the upper surface of the plate in the longitudinal direction of theplate, and said output electrodes includes two first output electrodesformed on the both confronting side surface in the longitudinaldirection of the plate.
 3. A Rosen type Piezoelectric Transformer withmultiple output electrodes according to claim 2, wherein said outputelectrodes further comprise a plurality of second output electrodes onthe upper side of the plate, wherein the distances between theneighboring electrodes being identical each other.
 4. A Rosen typePiezoelectric Transformer with multiple output electrodes according toclaim 1, wherein the piezoelectric transformer is made by multi-layeringfirst piezo-sheets printing both the input electrode and the outputelectrodes on the surface, and second piezp-sheets printing the commonelectrode on the surface in turn.
 5. A Rosen type PiezoelectricTransformer with multiple output electrodes according to claim 1,wherein said input electrode is formed on one end of the upper surfaceof the plate in the longitudinal direction of the plate, and saidmultiple output electrodes comprise a first output electrode formed on aside surface of the plate in a direction of thickness of the plate,adjacent to the other end of the upper surface of the plate, and atleast one second output electrode formed in a band shape, each secondoutput electrode being arranged apart in an equal distance between theinput electrode and first output electrode in the longitudinal directionon the upper side of the plate.
 6. A stabilizer for multiple lightsources, using a Rosen type Piezoelectric Transformer with multipleoutput electrodes, comprising: a rectifying section rectifying ACcommercial electric power source to DC electric power; a power factorcompensation section compensating the power factor caused by thefluctuation of the voltage of AC commercial electric power source so asto maintain the voltage of DC electric power generated from therectifying section in uniform level; AC voltage generating sectionconverting the DC power inputted from the power factor compensationsection to AC electric power having a predetermined frequency; and aRosen type Piezoelectric Transformer with multiple output electrodeshaving a identical band shape, wherein the output electrodes is arrangedin parallel to a input electrode, have an equal distance betweenneighboring electrodes, are electrically connected to a plurality ofcold cathode fluorescent lamps respectively; whereby identical voltagesare applied simultaneously to a plurality of fluorescent lamps.